Datasheet
Smart Sync
C 2
i
C 1
i
R 1
SET
R 2
SET
PTH08T220W
V
I
V
I
V
O
V
O
INH/ UVLO
INH/ UVLO
+Sense
–Sense
GND
Track SYNC TT
V Adj
O
V Adj
O
V 1
O
V 2
O
V
I
= 5 V
0
o
GND
PTH08T240W
+Sense
–Sense
GND
Track SYNC TT
180
o
GND
Vcc
GND
Q
Q
PRE
CLR
CLK
D
f
clock
= 2 Xf
modules
SN74LVC2G74
C 1
o
C 2
o
PTH08T220W , PTH08T221W
SLTS252K – NOVEMBER 2005 – REVISED JUNE 2009 ...................................................................................................................................................
www.ti.com
Smart Sync is a feature that allows multiple power modules to be synchronized to a common frequency. Driving
the Smart Sync pins with an external oscillator set to the desired frequency, synchronizes all connected modules
to the selected frequency. The synchronization frequency can be higher or lower than the nominal switching
frequency of the modules within the range of 240 kHz to 400 kHz. Synchronizing modules powered from the
same bus eliminates beat frequencies reflected back to the input supply, and also reduces EMI filtering
requirements. Eliminating the low beat frequencies (usually < 10kHz) allows the EMI filter to be designed to
attenuate only the synchronization frequency. Power modules can also be synchronized out of phase to minimize
ripple current and reduce input capacitance requirements. Figure 26 shows a standard circuit with two modules
syncronized 180 ° out of phase using a D flip-flop.
Figure 26. Smart Sync Schematic
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